Electronic switch



Oct. 9, 1951 CLARK 2,570,208

ELECTRONIC SWITCH Filed Oct. 8, 1947 DEFLE ON a VOL GE S RCE A TTOPNE'YPatented Oct. 9, 1951 UNITED STATES TENT OFFICE I ELECTRONIC SWITCHApplication October 8, 1947, Serial No. 778,574 In France August 21,1939 Section 1, Public Law 690, August 8, 1946 Patent expires August 21,1959 8 Claims.

The present invention relates to electronic discharge devices and moreparticularly to electronic discharge devices in which the discharge isconcentrated in one or more beams.

In devices of this kind it is often desirable to modify the beams aftertheir formation, for example, by deviation, or in some other way and,consequently, it is desirable to have beams which can easily becontrolled. With this object it is of interest that the beam or beamsshould consist of electrons having velocities comprised with in thenarrowest possible range, and as uniform a direction of velocity aspossible. These conditions have been realised in the majority of cathoderay tubes and related devices by using only a small proportion of thecathode to emit the electrons and amongst these electrons only those areused which seem to have velocities whose directions and magnitudes aresuitable for the desired object. Arrangements of this kind have thegreat disadvantage of decreasing useful electron currents to a very lowvalue. For example, a cathode with a normal oxide coating usually emitsa thermionic current of 50-100 milliamperes per heating watt. A cathodeof this type employed in a valve with beams controlled by deviation andheated with an energy of 2.5 watts would have a useful emission of only125 milliamperes and, moreover, in consequence of the speed conditionsto be satisfied, only about 1 per cent of this emission can be used inthe usual type of structures which form electron beams.

The invention has in consequence for its principal object the provisionof means for the production of one or more electron beams in which thevelocities of the electrons are substantially parallel in directions andof magnitudes comprised within a narrow range of values, whilst reducingthe los in energy to a considerable extent, in other words by markedlyincreasing the useful current of electrons emitted by the cathode, andconsequently the resultant output of the discharge device.

Further, if electronic discharge devices where the beam or beams ofelectrons are to be subjected after their formation to means ofdeviation, whereby they are deflected as desired to one or other of acertain number of targets, or collector electrodes, while the focusobtained on one of the targets is assured. it is desirable to maintainthis focus substantially constant, irrespective of the target on whichthe beam is made to fall. In order that the focusing action of thedeflecting means shall be substantially uniform independently of thedeviation imposed on the beam, or beams, these means of deflectionshould have the maximum action possible on the electrons of the beams,that is to say that the speeds of the electrons at the locations wheremeans of deflection begin to act in the completed structure of thedischarge device should be as slow as possible. Moreover, as it isobvious that these means of deflection will not act in a uniform manneron the electrons of a beam of relatively large transversal dimension,the beam or beams generated should be concentrated as much as possibleso as to reduce to a minimum the differences of the forces of deflectionon the various electrons of the beam.

The invention has, consequently for another of its objects, theprovision of means to produce one or more electron beam comprising attheir output from the emissive and beam focusing structure, electrons ofsubstantially uniform velocities of low values, and of directions whichare substantially parallel, concentrated in a very small transversalsection, and all these accomplishments using a reduced number ofelectrodes in the generator structure of the beam, or beams.

The beam electronic discharge device in accordance with the presentinvention comprises means for the limitation of the discharge of acathode according to one or more determined beams, means to ensuretheflow of the electrons from the said cathode, and to give them avelocity and direction which is substantially uniform, and means forslowing down the electrons in such a way as to ensure at the output ofthe emissive and beam focusing structure a point of concentration ofeach beam at which the electrons have a minimum speed and thispreferably in such a manner that the point where each beam convergesshould also be a point where the paths of the electrons emitted by thesurface of the corresponding cathode cross one another, that is to say,a point where the electrons emitted by the portion on the left of theemissive surface pass substantially to the right of the beam, and viceversa.

In a more specific manner an electrode structure according to certaincharacteristics of the invention which generates one or more electronbeams comprises an electrode which is an emitter of electrons or acathode, and a oollimating electrode around this cathode having one ormore openings for the passage of the electrons intended to form thebeam, or beams, an accelerating electrode around the first twoelectrodes, and an electrode surrounding the first three and having oneor more openings in alignment with those of the collimating electrodearranged to reduce the speed of the electrons without essentiallymodifying the direction of their velocities which are in the desireddirection of propagation. The voltages of these electrodes are regulatedin such a manner as to ensure a point of'convergence of electron pathand preferably of intersection in a location situated in the immediatevicinity of the opening, or openings of the electrode which retards theelectrons. The collimating electrode is brought to a negative potential,or zero with relation to the cathode, the accelerator electrode servingto ensure that the electrons will be withdrawn from the immediatevicinity of the cathode is carried to a positive potential with relationto the cathode and the electrode which retards the electrons is broughtto a potential lower than that of the accelerator electrode, thispotential being positive, negative or zero with relation to that of thecathode, to determine the crossover point of the beam, or beams anddepending upon the desired mean speed of the electrons.

In accordance With another characteristic of the invention, theaccelerator electrode comprises an electrode in the form of a grid withlarge meshes or other structure having large openings, having the planeor substantially plane portion of their surface in front of thoseportion of the surface of the cathode which emit the useful electrons.

In accordance with another characteristic of the'invention, theaccelerator electrode comprises portions which are substantially plane,and have large openings placed in front of each active portion of thecathode, these portions being electrically independent of one another,and may be employed to accelerate or block the corresponding electron byvariations in the potentials which are individually applied thereto.

In accordance with another characteristic of theinventior nthecollimating electrode is an integral part of the cathode, whichtherefore has non-emissive portions so arranged as to play the part ofthe collimating electrode in relation to the emitting portions. I

The invention, will, moreover, be explained in detail in thefollowingdescription of examples of embodiments exemplified by theattached drawings, in whichf v I v Figure 1 shows an electrode structureincorporating characteristics of the invention shown by way ofillustration as being part of a structure of an electronic dischargedevice withradial deviation or deflection of the electronic beam.

Figure 2 shows a modification of the electrode structure as an object ofthe invention;

Figure 3 shows an electrode structure according to the characteristicsof the invention for the production of two opposed electron beams and;

Figure 4 shows a modification of the structure of Figure 3 comprising,in accordance with another characteristic of the invention, means tocontrol independently of the two electron beams produced by thestructure.

Figure 1 shows schematically a generating structure of a beam ofelectrons incorporating certain characteristics of the invention to beemployed in a radial deviation device with low potential. It is clear,nevertheless, that the invention is in no way limited to the type ofdeviation which is shown here, only to give an example of theapplication in practice of such an electrode structure. A 7

In the different figures, moreover, the corresponding element areindicated by the same reference numbers.

An electrode or cathode emitting electrode, either of the direct heatingtype or indirect heating type is shown schematically in 4. Thiselectrode is surrounded partially by an electrode I having one or moreopenings such as 8, Figure 1, or S and 8, Figures 3 and 4. As shown, thielectrode I may consist either of a cylinder or a sphere open at 8 andcentered on the cathode 4 as in Figure 1, or in several cylinder orspherical portions centered on the cathode according to the number ofelectronic beams desired. Therefore, Figures 3 and 4 show this electrodedivided in two portions because these examples of embodiments have beenchosen in the case where it is desired to obtain two opposed beams.

This electrode I, or collimating electrode, is taken to a negativepotential with respect to the cathode in order to ensure theconcentration of the electrons emitted by the cathode along the paths ofits opening 8, or of its openings 8 and 8-.

Around these two electrodes is arranged an accelerator electrode 2 takento a positive potential with respect to the cathode, in such a way as tocreate a large gradient of potential in the desired direction ofdisplacement of electrons, in other words, in such a way as to ensurethat the electrons will be removed from the immediate vicinity of thecathode surface and to avoid the formation of an electronic space chargein front of the surface of the cathode 4, at the same time giving to theelectrons a component of speed in this direction which is great withrespect to the speeds of any directions in which they have been emitted.

In order not to impede the paths of the electrons emitted by'the'c'athode 4, this accelerator electrode 2 has wide openings,forexample, consisting of alarge mesh grid, or an assembly of wiresWhichare relatively thin in 'relation to their spacing. This acceleratorelectrode 2 is arranged so as to have a substantially plane surface 9 infront of the active portion of the cathode, the rest of the electrode isof cylindrical or spherical form as shown in Figure 1, or symmetricalwith relation to the'lat'eral supporting rods H) as shown in Figure 2,or again having two plane surfaces 9 and 9" in front of the activeportions of the cathode, as shown in Figure 3. In a general way theaccelerator electrode will have as many substantially plane surfaces asthere are electron beams in the beam forming structure.

An electrode 3 consisting of a cylinder or of a sphere, or othersuitable form provided with openings ll, Figures 1 and 2, and ll'-l'l,Figures 3 and 4 in" alignment with the openings of the electrode Isurrounds the preceding electrodes. This electrode 'is taken to a lowerpotential than that of the electrode 2,a potential which may bepositive, negative or zero with respect to that of the cathode 4according to the choice of potentials of theelectrodes I and 2, of thediameter of electrode 3, and of the dimension of the opening or of theopenings 8, 8 andlLH. 'H

With such an electrode structure the beam or beams at the outlet of thestructure has a marked focal point for the electrons which have slowspeeds and uniform or substantially uniform direction and which will beparticularly suitable for. further control such as a deviation. Forexample, as shown in Figure l, the electron paths which are extremelynarrow and concentrated 5 at 12, as indicated in dotted lines at 13 arefocused by the choice of potentials applied to the electrodes I to 3 tosuch a degree that the electrons emitted from the right side of thesurface of the cathode 4 and passed to the left side of the beam andvice versa, can then be subjected to a radial deviation field, betweenthe electrodes 5 and E. This radial field is established by applyingpotentials in such a way as to re-accelerate the electrons and may becreated by carrying the electrode 5 to a potential which is verypositive with respect to the cathode and simultaneously the electrode 6to a potential below that of the electrode 5, and which may even be zeroor negative with respect to the cathode 4. The direction of thevelocities of the electrons of the beam at the outlet of the structure Ito 4 is substantially tangential to the cylindrical electrode 5 and thebeam is concentrated at 127 approximately from the point 12 and thus onone of the collector electrodes la to Fe according to the potential ofthe cylindrical electrade 6 as is known in the art. In the applicantsembodiment, for example, a current of 2 milliamperes was transmitted tothe collector electrodes 7 when a voltage of 360 volts was applied tothe electrodes 5 and I, a normal zero voltage to the electrode 8, +15volts on the electrode 3, +25 volts on the electrode 2, and 250 volts onthe electrode I. This electronic current was confined to 1 mm. in widthat the point of impact. If the potentials were adjusted in such a waythat the width of the beam was 2 mm. a current of 5 milliamperes couldbe passed to the collecting electrode. intensity of its current do notdepend upon the voltage of the electrode 6, even though this voltagedetermines the point of impact on the beam on the electrodes Ia-4e.

Instead of creating a crossover of the electrons of the beam at thepoint of convergence l2, it is clear that in certain cases a very highconcentration assuring a slow electron beam which is extremely narrowmay sufiice, as indicated in It and I4 on Figure 3.

The modification shown in Figure 2 of the structure 1 of Figure 1 ischaracterised by the fact that the collimating electrode l of Figure 1has been incorporated with the cathode 4, that is to say, that thecathode 5 has been provided in such a form that it constitutes at thesame time an emitting cathode of electrons on a portion 15 at the side Aof the structure, and a collimating electrode for the emitted electronscreated for example, by the projecting portions [6 of each side of theemissive portion IS. The rest of the cathode on the side B of thestructure is not coated with emissive substance. This modification ofthe structure is evidently not limited to that shown on Figure 2, but itmay be seen that it may be applied to structures with multiple beams,and that there may be a great number of suitable forms of cathodes.

The width of the beam and the iii) In Figure 4 has been represented anaccelerator electrode in two parts 2 and 2 which are mechanicallyindependent. These two parts may well be electrically independent ifdesired, which may permit chosen potentials to be a p ied to them indifferent ways. In particular these potentials may be such that one ofthe portions. 2 or 2 mav act in order to accelerate the electronsemitted by the side corre ponding to cathode 4, whilst the other portionsubstantially impedes the pa sa e of the electrons emitted by the otherside of the structure. Such an arrangement, which may be extended todevices with beams of a greater number than two may be employedparticularly advantageously in electronic switching systems orequipments of the push-pull type, and the like.

It is clear that the invention is not limited to examples of embodimentsshown and described, but may on the contrary be capable of manymodifications, in particular, in the form of the electrodes shown, theseelectrodes being able to be square, rectangular, cylindrical,ellipsoidal, oval or other forms without changing the operation of themodified structure. It is also clear that it may be employed in deviceswith any number of electron beams, and is moreover, not limited to itsuse with radial deflection structures as already stated. Still othermodifications and adaptations will become apparent to the expert withoutdeparting from the scope of the invention.

What is claimed is:

1. An electron discharge device comprising a cathode, means forassisting the emission of electrons from said cathode, a collimatricelectrode positioned around said cathode and having an opening for thepassage of electrons to form a beam, an accelerating electrodepositioned around said cathode and collimatric electrode and held at agiven positive potential with respect to said cathode, and an electronretarding electrode held at a potential lower than said acceleratingelectrode surrounding said cathode and last two electrodes and having anopening in alignment with the opening in said collimatric electrode toreduce the speed of the electrons passing through said openings withoutmodifying the direction of those electrons which have the desireddirection of propagation.

2. An electron discharge device according to claim 1, in which saidcollimatric electrode is held no more positive than said cathode.

3. An electron discharge device according to claim 1, in which theaccelerator electrode is in the form of a grid with large meshes andhaving a substantially plane surface in front of the cathode.

4. An electron discharge device according to claim 1, in which thecollimating electrode is an integral part of the cathode but isnon-emissive.

5. An electron discharge device according to claim 1 in which saidcollimatric electrode and said retarding electrode each have anadditional opening substantially oppositely disposed with respect tosaid first mentioned openings to form an additional electron beam ofreduced electron velocity adjacent said additional openings.

6. An electron discharge device according to claim 1 in which saidretarding electrode has an additional opening substantially oppositelydisposed with respect to said first mentioned openings, and saidaccelerating electrode comprises two electrically isolated portions eachpositioned in line with a respective opening in said retardingelectrode.

'7. In an electron discharge device, a cathode,

beam forming means for limiting the emissionof electrons to a givenportion of said cathode and to focus the beam through a crossoveradjacent said cathode, electron retarding means positioned adjacent saidcrossover and spaced further from said cathode than from said beamforming means for reducing the velocity of said electrons approachingsaid crossover, electron accelerating means positioned between saidcathode and said crossover, a plurality of electron collecting elementspositioned to one side of said cathode, two partially cylindricalcoaxial electrodes having difierent radii the opposing arcuate surfaceof which define an arcuate space to receive the beam, first voltagemeans for establishing a steady potential difference between saidcoaxial electrodes, and second voltage means for applying a varyingpotential difference between said coaxial electrodes to direct said beamto selected ones of said collecting elements.

8. In an electron discharge device, a cathode, beam-forming meansincluding an accelerating electrode for limiting emission of electronsto a given portion of said cathode and to focus the beam through acrossover adjacent said cathode, electron retarding means positionedadjacent said crossover and spaced further from said cathode than fromsaid beam-forming means for reducing the velocity of said electronsapproaching said crossover, electron-accelerating means positionedbetween said cathode and said crossover, a plurality of electroncollecting elements positioned to one side of said cathode, twopartially cylindrical co-axial electrodes having different radii theopposing arcuate surfaces of which define an arcuate space to receivethe beam, positioned so the crossover occurs between said surface and asource of varying D. C. voltage connected between said partiallycylindrical electrodes to direct said beam to selected ones of saidcollecting elements.

TREVOR H. CLARK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,979,392 Lubcke Nov. 6, 19342,100,701 Schlesinger Nov. 30, 1937 2,107,520 Schade Feb. 8, 19382,144,085 Rothe et al Jan. 17, 1939 2,159,765 Jonker et a1. May 23, 19392,197,033 Diels Apr. 16, 1940 2,252,580 Rothe et al Aug. 12, 19412,254,096 Thompson Aug. 26, 1941 2,380,225 Fleming-Williams July 10,1945 FOREIGN PATENTS Number Country Date 475,106 Great Britain Nov. 12,1937 498,167 Great Britain Jan. 4, 1939

